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When conducting a modal test on a fan with free-free boundary conditions, it is recommended to perform the test on the impeller mounted on the shaft. However, some may wonder why tests are often conducted on the impeller alone. Can anyone shed light on this discrepancy? Thank you.
Dave, if you are worried about the small raised blades on a fast-spinning wheel, the shaft's impact is likely minimal. However, if you are interested in the wheel's different modes (1D, 2D, etc.), then the presence of the shaft becomes essential. I recommend conducting all testing with the shaft in place, as it provides the true foundation from which the impeller will operate. - Ron Brook
Ron conducted a thorough modal analysis on the impeller and shaft, producing a visually impressive animation. If you would like, I can send the AVI file to a secure email address.
Answer: - Modal tests are often conducted on the impeller alone to isolate the structural dynamics of the impeller without interference from other components such as the casing or shaft. This allows for a more accurate and focused analysis of the impeller's natural frequencies and mode shapes.
Answer: - By conducting modal tests on the impeller alone, engineers can gain insights into the impeller's structural response to excitation forces, identify potential mode shapes that may lead to resonance issues, and optimize the impeller design for improved performance and reliability.
Answer: - Testing the impeller alone can help in identifying critical modes that are specific to the impeller design, enabling targeted modifications to enhance the impeller's structural integrity and vibration characteristics. Additionally, focusing on the impeller simplifies the modal analysis process and facilitates more efficient troubleshooting of vibration problems.
Answer: - While testing the impeller alone provides valuable insights into its dynamic behavior, it is essential to consider the interactions between the impeller and other components in the complete fan system during operation. Therefore, follow-up tests on the assembled fan may be necessary to validate the findings from